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Mid-IR Spectra of AGB and Post-AGB Stars

Published online by Cambridge University Press:  07 August 2017

C. J. Skinner ,
M. J. Barlow ,
K. Justtanont  and
R. J. Sylvester
C. J. Skinner
Affiliation:
Institute of Geophysics & Planetary Physics, L-413, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA94551-9900, U.S.A.
M. J. Barlow
Affiliation:
Dept. of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, Great Britain
K. Justtanont
Affiliation:
Dept. of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, Great Britain
R. J. Sylvester
Affiliation:
Dept. of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, Great Britain

Extract

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We have generated models of complete nova energy distributions, including the effects of the nova dust shell emission and absorption. In order to account for the dust, we require optical constants throughout the UV and EUV. Draine & Lee (1984) is the only source of such data for silicates. However, their ‘astronomical silicate’ has a strong resonance in the UV which causes circumnova dust to be heated far above its sublimation temperature in our models of Nova Her 1991. We have therefore recalculated the silicate optical constants, using the Kramers-Kronig relations, including a λ−1.0 far-IR dependence and improved 9.7μm feature, and decreasing the UV and EUV efficiencies of the grains. With these new silicate constants we can reproduce the observed behaviour of the dust shell in Nova Her 1991. Since our optical constants are consistent with the behaviour of Nova Her 1991, an EUV source, they should also be appropriate for the treatment of PN.

Type
IV. Planetary Nebulae Connection: Evolution from the AGB
Information
Symposium - International Astronomical Union , Volume 155: Planetary Nebulae , 1993 , pp. 321
Copyright
Copyright © Kluwer 1993 

References

Draine, B. T., Lee, H-M.: 1984, ‘Optical Properties of Interstellar Graphite and Silicate Grains’, Ap. J. 285, 89 Google Scholar
Justtanont, K., Barlow, M. J., Skinner, C. J., Tielens, A. G. G. M.: 1992, ‘The Nature of Dust around the Post-asymptotic Giant Branch Objects HD161796 and HD179821’, Ap. J. 392, L75 Google Scholar